Carburetor



Dec. 5, 1939. M. MALLORY 2,132,090

CARBURETOR Filed Oct. 21, 1936 Patented Dec. 5, 1939 UNITED STATESPATENT OFFICE 4 Claims.

to means for controlling the mixture ratio as the position of thethrottle and the load vary.

The primary object of the invention is to pro- 7 vide a carburetor ofsimple construction, in which the mixture ratio is automaticallycontrolled to insure smooth and economical operation during variationsin the throttle opening and in response to variationsin engine speed andload.

A further object of the invention is to provide improved means whereby,upon an increased throttle demand, the mixture will be enrichedtemporarily until there is a corresponding increase in the speed of theengine.

A still further object of the invention is to provide improved means foradjusting the mixture ratio as affected by an increase in the throttleopening.

The specific construction of the invention in its present embodiment andthe principles governing its operation will be more particularlyexplained in connection with the accompanying drawing in which- Fig. 1is. a verticalsectional view taken centrally of a carburetor constructedaccording to. the invention. V

Fig. 2 is an enlarged sectional detail view taken on the line 22 of Fig.1, showing a means for adjusting the mixture ratio for the higherspeeds.

The invention is illustrated in the drawing as applied to a down draftcarburetor, which has an air inlet 5, a mixing chamber 6, and a fuelmixture outlet 1 adapted to be connected with the engine intakemanifold. The mixing chamber 6 is formed with a venturi '8 and fuel isdischarged into the center of this venturi through a jet nozzle 9 from awell l0. The fuelis supplied to the'well I0 through a passage II from abowl l2, to which the fuel'is admitted through a conduit i3 and a valvel4 controlled by float IS in the usual manner.

The fuel mixture outlet 1 is controlled by a main throttle valve l6mounted on a stem II, which is provided with an arm l8 connected to athrottle control rod l9. A link 20 connects the arm l8 to a metering pin2| provided with a fiat taper 22, which opens the port 23 leading to thenozzle 9 in synchronism'with the opening of the throttle valve I6.

An air valve 24 mounted on a stem 25 controls the direct admission ofair to the mixing chamber 6. An arm 26 is securedrto the stem 25. A rod21 pivotally connected to a rearward extension 28 of the arm l8telescopes into theend of a rod 29 which is pivotally connected to thearm 26 and is provided with an adjustable stop nut 30.

Thus it "will be seen that, when the throttle valve I6 is closed, thevalve 24 will be positively 5 closed in synchronism therewith. If thevalve l6 is opened slowly, the valve 24, which is unbalanced,*will openat the same time, due .to air flow and pressure thereon. If the valve I6 is 'opened quickly, however, the valve 24 will lag be- 10 hind, duetothe influence of a dash pot, which comprises a piston 3| reciprocable ina cylinder 32 and connected by a connecting rod 33 to the arm 26. Thepiston 3| is provided with a relief vent 34 covered by a valve 35 topermit its ready return when the throttle is closed.

A venturi 36 is formed in the air inlet passage above the valve 24 andan air passage 31 with an outlet 38 into the venturi connects the latterto the lower end of the dash pot cylinder 32. As 20 the throttle valveI6 is opened .for acceleration, the lagging of the valve 24 creates anincreased vacuum in the vicinity of the nozzle 9, thus temporarilyenriching the mixture without imposing a permanent load'upon the valve24 and without 25 the necessity of using an accelerating pump, until theengine picks up speed, thereby increasing the suction through theventuri 36 and through the passage 31. This in turn hastens the open-.ing of the valve 24, relieving the increased vac- 30 uum around thefuel nozzle and restoring the normalmixture ratio. An adjusting screw39, extending into the passage 31, determines the rate at which the dashpot permits the valve 24 to open in response to an increase in the main35 throttle opening.

.As the throttle is opened, the mixture depends in part upon the degreeof vacuum around the nozzle 9. If the ultimate opening of the valve 24with reference to the valve I6 is decreased, the 40 vacuum will beincreased and the mixture enriched. In order that this may be adjusted,the arm 26 is provided with a longitudinal slot 40. The pin 4|, whichreceives the end of the connectlng rod 33, is as shown in Fig. 2, in theform 5 of a shouldered stud 42 with a threaded end-secured in the slot40 and is adjustable longitudinaly thereof. Thus, by adjusting the pintoward the outer end of the slot, the mixture may be enriched and byadjusting the pin in the opposite 50 direction, it may 'be made leaner.

A by-pass 43 is connected at its-lower end to the fuel nozzle 9 and atits upper end to a nozzle 44, which projects into the upper venturi 36.The eflective capacity of this by-pass is adjusted by a screw 45. whenthe throttle is in idling position, air is drawn through this by-passand mixes with the fuel discharged from the nozzle 9 to form when thevalve I6 is opened, thereby restricting the supply of air to the fuelmixture.

In order to control the mixture ratio automatically during variations inthe throttle opening and in response to variations in engine speed, theinvention comprises a main throttle valve and an air valve with a fueljet nozzle between them. The main throttle valve, which is on the engineside of the fuel nozzle, is positively actuated through the throttlecontrol rod. The air valve, which is unbalanced, is positively closed bythe closure of the main throttle valve, but is opened only by air flowor suction. A dash pot connected to the air valve retards the opening ofthe latter if the main throttle valve is opened quickly, therebymaintaining a suificient suction.

around the nozzle to temporarily enrich the mixture until the enginepicks up speed. Unlike a spring loaded valve, however, the dash pot doesnot impose a permanent load and does not permanently increase the vacuumaround the fuel nozzle. 7

In the operation of noted that all of the fuel foridling, foracceleration or for operating under a heavy load is always supplied fromthe well It) through a single port to the nozzle 9. No accelerating pumpor power jet piston is necessary. The fuel is metered by the pin 2| inproportion to the opening of the throttle valve 16.

The air for the idling mixture is drawn through the by-pass 43 and mixeswith and atomizes the fuel before it leaves the nozzle 9. As the valvesl6 and 24 are opened, there is a suction through the venturi 36 which,as the speed increases, becomes suflicient to stop the air flowthrough.the by-pass 43. The suction through the venturi 8 is thensuflicient to atomize the fuel as it leaves the nozzle 9.

Since the unbalanced valve 24 may be opened only by air flow orpressure, if the throttle valve I6 is opened quickly, the valve 24,temporarily retarded by the dash pot, lags behind the valve l6 until theengine picks up speed. The suction developed by the increasing speed ofthe engine first acts directly upon the valve I6 and then,

as suction is developed through the venturi 36 and in the passage 31,accelerates the bleeding of the dash pot. As a result, the mixture istemporarily enriched for acceleration without the use of an acceleratingpump. Since the .yalve 24 is not spring loaded, the mixture ratio againbecomes normal as soon as the desired acceleration is effected. If,however, it should be desirable to have a slightly richer mixture forhigh speed, this may be obtained by adjusting the pin 4! so that thevalve 24 will not open as wide as the valve l6. This increases thesuction around this carburetor, it will be the fuel nozzle 9, with aconsequent increase in the mixture ratio. 4 While I have shown anddescribed in detail one specific embodiment of the invention, it is tobe understood that this is merely illustrative and that the inventionalso embraces such modifications as may be made within the scope of theappended claims.

Having thus described the invention, what I claim as new and desire tosecure by Letters Patent, is: y

l. A carburetor comprising a fuel mixture chamber with a venturi havinga fuel inlet, an air inlet, and an outlet adapted to be connected to anengine intake manifold, a main throttle valve controllingsaid outlet, anunbalanced valve controlling the air inlet, a dashpot tending to retardthe opening of the unbalanced valve, means for closing both valves inunison, said means serving to open the throttle valve but held, out ofoperative relationship with the unbalance. valve during opening movementof the throttle valve, another venturi on the atmospheric side of theunbalanced. valve, and a passage connecting the dash pot to the lastmentioned venturi, whereby suction through the said venturi tends toaccelerate the movement of the piston as the unbalanced valve opens.

. 2. A carburetor comprising a passage having an air inlet and a fuelmixture outlet with two venturis between them, a fuel supply duct with anozzle discharging into the second venturi, a main throttle valve on theengine side of the second venturi,'an auxiliary unbalanced valve betweenthe first venturi and the fuel nozzle adapted to be opened by air flowand pressure alone, an idling air by-pass from the first venturi intothe fuel supply duct, and means for positively closing the unbalancedvalve in synchronism with the closure of the main throttle valve, saidmeans serving to open the throttle valve but being out of operativerelationship with the unbalanced valve during said opening movement.

.3. A carburetor comprising a passage having an air inlet and a fuelmixture outlet with two venturis between them, a fuel supply duct with anozzle discharging into the second venturi, a

main throttle valve on the engine side of the second venturi, anauxiliary unbalanced valve between the first venturi and the fuel nozzleadapted to be opened by air flow and pressure alone, a dash pot with apiston connected to the unbalanced valve to retard the opening of thelatter, means for bleeding the dash pot into the first venturi, andmeans for positively closing the unbalanced valve in synchronism withthe closure of the main throttle valve.

4. A carburetor comprising a passage having an air inlet and a fuelmixture outlet with two venturis between them, a fuel supply duct with anozzle discharging into the second venturi, a main throttle valve-on theengine side of the sec.- ond venturi, an auxiliary unbalanced valvebetween the first venturi and the fuel nozzle adapted to beopened by airflow and pressure alone, a dash pot with a piston connected to theunbalanced valve to retard the opening of the latto the opening of themain throttle valve.

MARION MALLORY;

